Introgression and Pyramiding of Novel Resistance Genes for Diploid Potato Breeding

Late blight, caused by the oomycete pathogen Phytophthora infestans, is one of the most economically significant diseases of potato (Solanum tuberosum), leading to widespread yield losses globally. This research aims to introgress and pyramid novel late blight R-genes from wild species, Solanum pinnatisectum, Solanum venturii, and Solanum microdontum with other late blight R genes into cultivated diploid breeding lines of potato. Two accessions of S. pinnatisectum (PI275232 and PI275233) were screened for Rpi-blb3 and the novel Rpi2 genes, while MSKK1819, a breeding line with S. venturii background, was screened for Rpi-vnt1 gene. Three individuals (PI275232-6a, -8a, -9a) tested positive for Rpi-blb3 DNA marker, and four individuals from PI275233 (PI275233-1, -5, -7, -10) tested positive for Rpi2 DNA marker. Additionally, three individuals (MSKK1819-1, -4, -7) were DNA marker-positive for Rpi-vnt1. These lines are being evaluated for foliar resistance using detached leaf assays (DLA) with two P. infestans strains: US-23 and NL13316. PI275233 showed full resistance to US-23, however moderate resistance to the more aggressive NL13316 strain was observed. The Rpi-vnt-1 positive lines are currently being evaluated. To introgress the R genes from S. pinnatisectum, successful crosses were made using two S. verrucosum-derived bridge parents (MSJJ1821-01F2-049 and MSJJ1821-01F2-121). These progeny from the bridge crosses will facilitate the introgression of Rpi-blb3 and Rpi2 genes into diploid potato germplasm. Our ultimate goal is to pyramid the late blight R genes for durable late blight resistance.